Human In Vitro Fertilization (IVF) and Embryo Transfer (ET), first successfully performed in 1978, has become a widely practiced procedure to treat infertile couples who have failed with more conventional methods of therapy such as superovulation and intrauterine insemination. The most common indications for IVF and related procedures, such as Gamete In Vitro Fertilization or Gamete Intra-Fallopian Transfer (GIFT) which includes women having blocked or damaged fallopian tubes, and includes low sperm and/or egg quality. Related factors include age of the female, and the degree of endometrial receptivity. The procedure may also be used in cases of severe male factor where direct (intracytoplasmic) injection of sperm is an option. Another indication for the procedure is when the shell of the egg is abnormally thick, thus preventing the fertilized and dividing early embryo to escape and implant into the uterus. Creating a small opening through the shell has been shown to increase implantation rates. IVF is also being used when clinical or genetic factors require implantation of donor eggs from a fertile female that are fertilized in vitro and implanted into the recipient female using standard techniques.
The IVF/ET procedure typically involves the hormonal stimulation of the female to first suppress her ability to ovulate on her own, then stimulate development of follicles in the ovaries with a fertility medication. The mature eggs are removed from the ovary transvaginally using a needle, preferably guided under ultrasound. Following harvesting of the eggs, the eggs are identified and sorted with regard to maturity, and then placed with a sperm sample from the male. Approximately 24 hours after fertilization, the eggs are examined to confirm fertilization, which occurs in approximately 65% to 85% of the eggs harvested. After a short development period, the embryos are transferred, along with a volume of fluid, to the uterus using a delivery catheter. The delivery catheter is made of a soft plastic material to avoid damage to the endometrium.
There are many potential difficulties in achieving a successful implantation. Because of the soft nature of the standard delivery catheter, in a number of cases, the tip of the catheter may bend back on itself or curve away from the fundus of the uterus. The tip may also accidentally pass between the layer of the endometrium and myometrium. Conversely, a stiffer catheter increases the risk of trauma to the uterus or cervix, with the latter possibly leading to the release of prostaglandins and expulsion of the eggs from the endometrium.
One particular difficulty is the environment in which the catheters must function. Cervical tissue is mucousal, and the guiding catheter may become encumbered with mucus or blood when it passes through the opening of the cervix. As a result, the transfer catheter may become covered or clogged with mucus when it clears the guiding catheter. The mucus may then interfere with the transfer of the embryos, with the possibility of the embryos sticking to the mucus and not being transferred to the uterus. Other undesirable possibilities include subsequent transfer of embryos to the cervix or even to the vagina upon withdrawal of the catheters.
Several unsuccessful attempts have been made to improve success rates. U.S. Pat. No. 6,165,165 uses a guiding catheter and an implant catheter, the implant catheter made from materials of two different durometers, so that the stiffness of the catheter decreases from the proximal end to the distal end of the catheter. The resulting catheter may be easier to guide, but is still subject to interference from mucus. WIPO International Patent Applications WO99/37348 and WO01/74417 attempt to solve the problem with an end cap on a guiding catheter that swings open to allow the transfer catheter to pass through an opening and transfer the embryos. Alternatively, the transfer catheter may have a side port rather than an axial port on the distal end, so the side port will avoid interference from mucus. These embodiments are still subject to interference from mucus.
One way to increase the likelihood of success is to tailor the catheters used to the person undergoing the treatment, i.e., by using different lengths of catheter. These attempts to tailor the catheters have led to a proliferation of lengths of catheters, especially in guide catheters. Even with overnight delivery of the desired resources, this results in the need for hospitals and clinics to inventory more catheters and more sets of catheters than is desirable. In addition, these procedures are recognized as being very expensive. While catheters are not a major component of the cost of these procedures, anything that can help control their very expensive costs will be welcome. What is needed is a catheter system that can accomplish embryo implantation while helping to minimize costs and without the need for carrying many lengths of catheter sets.
What is needed is a catheter system that can increase the likelihood of successful embryo implantation patients desiring this procedure without interference from mucousal matter. What is also needed is a catheter system in which the catheter length may be varied without undue cost penalties.